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I'm guessing your misfire is due to the engine running lean. If you look at your fuel trims, both the short term (ST) and long term (LT) are negative which means the computer is reducing the amount of fuel actually injected compared to the correct calculated amount. Since both trims are negative they are added together which means the computer is reducing fuel by 30% in some instances you posted. The computer determines the correct about of fuel from the preprogrammed "map" based mostly on engine temp, rpm, and MAF reading. The O2's are what "trim" the fuel from the map based on their readings.
Soooo, after all this I'm going to guess your MAF is failing. Positive fuel trims are usually the result of a vacuum leak. The computer adds extra fuel to compensate for the extra air that isn't measured by the MAF. Negative fuel trims like you have indicate there is less air in the engine than was measured by the MAF, which really isn't physically possible. Your MAF is giving errant readings.
I'm guessing your misfire is due to the engine running lean. If you look at your fuel trims, both the short term (ST) and long term (LT) are negative which means the computer is reducing the amount of fuel actually injected compared to the correct calculated amount. Since both trims are negative they are added together which means the computer is reducing fuel by 30% in some instances you posted. The computer determines the correct about of fuel from the preprogrammed "map" based mostly on engine temp, rpm, and MAF reading. The O2's are what "trim" the fuel from the map based on their readings.
Soooo, after all this I'm going to guess your MAF is failing. Positive fuel trims are usually the result of a vacuum leak. The computer adds extra fuel to compensate for the extra air that isn't measured by the MAF. Negative fuel trims like you have indicate there is less air in the engine than was measured by the MAF, which really isn't physically possible. Your MAF is giving errant readings.
Thanks for the information, I'll check the MAF sensor to see if its failing, I hope this isn´t the case since a MAF sensor is pretty expensive.
Could you record the data in tech stream? The screenshots help see that some things are off - B1 o2s1, temperature looks low, is the air temp really 40 degrees or is that just car sitting still engine on, hood closed?
Anyway to get the data from cold please connect techstream to the car - ignition on/engine off. Create custom list
Then go to record snapshot (it's in the drop down menu somewhere)
change the recording duration to 10+minutes (whatever you desire, I usually have mine set to max) and click the record button
Start the car
After a few minutes - say 4 minutes assuming it is warming up ok - raise the engine to 2500 rpm for about 20 seconds and let it return to idle. Repeat this 2 or 3 times.
If you can go for a short drive. If not - won't really matter.
Then when done click stop recording and export the datafile (csv). Save it somewhere you can find it easily.
With that we can make some charts - either upload your csv here, or have a go making charts with it in excel (or other program).
Here is a chart from a quick warmup data I made an hour ago.
Oh yeah and what ever you do - don't go and buy a fake MAF sensor off ebay, especially if they are cheap.
Wit until we can see what is going on.
This is the information that I got from exporting the file, my techstream for some reason didn't allow me to record 10 minutes straight, it was fixed at 5 minutes, but it didn't record 5 minutes of data, it recorded 2:30 minutes of data, so I recorded this information 5 times. If this doesn't work I have the original file from techstream, but this forum doesn't let me upload it.
This is the information that I got from exporting the file, my techstream for some reason didn't allow me to record 10 minutes straight, it was fixed at 5 minutes, but it didn't record 5 minutes of data, it recorded 2:30 minutes of data, so I recorded this information 5 times. If this doesn't work I have the original file from techstream, but this forum doesn't let me upload it.
The coolant temperature is in celcius, techstream recorded it like that for some reason, algo, on the last recording my techstream crashed, so the information probably isnt the 2 and a half minutes long.
Oh yeah and what ever you do - don't go and buy a fake MAF sensor off ebay, especially if they are cheap.
Wit until we can see what is going on.
Also, you said that 40 degrees was too cold, the techstream is recording it in celcius. Since you are from Australia I think that you guys use celcius also, did you think the info was in farenheit? If not, is 40 degrees celcius too cold for that sensor?
Perfect. I am assuming you haven't reset the computer judging by the LTFT values that it started out with which means there are preexisting compensations in the program.
A couple of things. - Yes in Australia we use the metric system so degrees celcius.
The good news is it looks like you temperature sensor is good. Also it looks like the maf is reading ok - certainly nothing that appears wildly out.
There are a lot of almost same data streams with slightly different names in techstream - ie the throttle position sensor. You grabbed "Throttle sensor position %" when I need to see "Throttle POS %". Subtle wording difference makes it tricky to get the right one and easy to get the wrong one. (See the data from my car to check). Reason being is POS it gives us the relative position in the sensor - eg sensors read 0-100. They are usually set to 15% at engine off when attached to the throttle body. This means that usual operation is in the 10-85% range to ensure that 0-10 or 85-100 is never used. This is a safety measure in the system to ensure that the computer doesn't suddenly accelerate/not accelerate from an electrical fault giving a false reading. ie if a sensor suddenly reads 0-.03 the car will go into limp home mode. Same if it gets values above 90% because it will treat the sensor data as suspect.
Moving on. O2's
There are a few things we can see here.
B1 O2S1 - something it definitely wrong - either dead sensor or broken wiring.
B1 O2S2 - Looks to be running lean, though spikes when revved which seems to be indicating that it works - to what extent I can't tell as the computer is leaning everything.
B2O2S1 - appears to be operating ok - however I'm not convinced that it is necessarily accurate because...
B2 O2S2 - hardly moves and is reading very lean
The sensor data stream is slightly different to the one I wanted but I think it is comparable. Eitherway the computer is over time leaning our bank 2. And enrichening bank 1. See how this correlates to the B1 O2s2 starting to read?
So could you make another set of data after a computer reset?
And or what's your plan with B1 O2S1?
**Definitely need to validate the circuit between the sensor connector and the computer, and or check the sensor itself electrically. I am assuming the sensor is dead, however you need to check that wiring**
Assuming it is dead I would probably plan to replace both front sensors with the correct denso sensors because the readouts from B2O2S1 don't correlate in any way to the secondary readings. B2O2S2. Sensor 2 is basically very lean the whole time - it should have some fluctuations during that duration given sensor 1 appears to be working correctly - This makes me skeptical of the data coming from the seemingly operational B2 02s1 sensor.
I'll disconnect the battery today (its 6:39 pm where I live) and tomorrow I'll do the live data test with the computer reset, and I'll look into the Throttle POS to see what name does it have on my techstream.
My plan with B1 O2S1 is to fix the problem, either by replacing the sensor with an OEM one or to replace the wiring.
Today I lifted the car up on jackstands and tried to disconnect the plug again, I bent the metal piece that you told me to bend and I had some extra room to work with. It was imposible to get the clip off, suddenly it broke and I was relieved because then I could disconnect the male plug from the female plug, but still the plug was stuck, I'm not sure why it's stuck still, the retaining clip is broken, it should be easy to disconnect, I tried to spray a little WD-40 but still I couldn't disconnect it. I didn't see another clip on the plug, tomorrow after getting the data I'll clamp a vice grip to the male plug and try to pry the plug out with a flat head screwdriver (hope I have the space).
When I changed mine a couple of years ago I did have to use a small screw driver as a lever to carfully separate the two halves of the plug. Bank 1 is especially difficult with that silly guard. B2 was easy peasy.
....anyway good luck with it. It will eventually just pop and separate.
When I changed mine a couple of years ago I did have to use a small screw driver as a lever to carfully separate the two halves of the plug. Bank 1 is especially difficult with that silly guard. B2 was easy peasy.
....anyway good luck with it. It will eventually just pop and separate.
Hello, I just connected the battery again and connected techstream to the car, while it was recording the data techstream crashed and it didn't record any data, I'll do the reset again later today. From what I could see, the O2 sensor B1S1 was still getting 1.27V even when the car was not started, also in my techstream I don't have a Throttle POS option, I found a throttle voltage % or something like that which in idle is around 15%, before starting the car it was at 19%.
Also I heard a crackling sound coming from under the car, the cat maybe.
Then:
check the connectors to the variable valve solenoids. Possibly even see how they respond to the solenoid test in tech stream. A broken vvt solenoid can mimmick a misfire.
if its not that you are left with fuel or compression.
check the connectors on injectors.
possibly swap injectors around if you have good oring handy. They will likely be hard and brittle with age unless recently replaced..
See how you go.
Originally Posted by YODAONE
Is this a temporary repair?
Worth replacing with correct factory hoses and hose clamps..engine will.perform better and .not expensive parts.
Have your mechanic check your Oil Control Valves.(OCV)
There are two oil control valves (OCVs) on your V-8 > one for each bank of cylinders. They should both be replaced. Replacing only one typically results in the same engine shake. When the oil control valves failed on my '01 LS430, I had codes P0300, P0301, P0303, P0305, along with P1349 (driver's side OCV).
01-05-21, 05:33 PM
